Gas testing tubes are used in a known manner for measuring the concentration of dangerous substances at a workplace and the spectrum of the gases and vapors to be determined is known and thereby the selection of corresponding measuring tubes based on earlier measurements of the occurring substances is known.
Certain difficulties occur when contaminants of an unknown type and concentration are to be detected without a complex precise determination of contaminants by means of laboratory measurements. The contaminants can, for example, occur at a special waste disposal facility or as a consequence of a chemical accident. In these applications, test tubes in a combined arrangement offer substantial time advantages when determining contaminants and the information which they provide can be used for evacuation measures which have to be rapidly initiated or the information provided can be used to exclude the possibility of evacuation because a corresponding danger is not present.
In such measuring devices, there are mostly several and sometimes up to twenty different test tubes which must be charged with the mixture to be investigated. For this reason and because the measuring results of the individual test tubes must be made available quickly and simultaneously and, if required, for further processing in an electronic evaluation apparatus, the problem is presented that an arrangement must be used having a high sensitivity for the individual test tubes. Furthermore, such an arrangement should afford the possibility of a rapid exchange of the test tubes in their entirety.
German Patent 26 26 600 discloses a measuring apparatus wherein several test zones are sequentially scanned by a common opto-electronic scanning device with selective illuminating and transmitting elements in the time-division-multiplex method. Such test strips having several reaction zones separated from one another are used for investigating liquids such as for medical urine tests.